Hello @twe
There are two parts that you need to check in the response:
<messages>
<resultCode>Ok</resultCode>
<message><code>I00001</code>
<text>Successful.</text>
</message>
</messages>
This section indicates that the transactions was succesfully processed by the processor.
The next section contains more detailed information including the response code:
<transactionResponse>
<responseCode>1</responseCode>
<authCode>08ZZBL</authCode>
<avsResultCode>A</avsResultCode>
<cvvResultCode>M</cvvResultCode>
<cavvResultCode>2</cavvResultCode>
<transId>2242960468</transId>
<refTransID />
<transHash>2BECB1ABE41E4714D138E45065B5DD24</transHash>
<testRequest>0</testRequest>
<accountNumber>XXXX1111</accountNumber>
<accountType>Visa</accountType>
<messages>
<message><code>1</code>
<description>This transaction has been approved.</description>
</message>
</messages>
</transactionResponse>
You need to look at both parts, the message and the transactionResponse. There are also settings in the merchant interface which allow control over which responses are accepted, held for review or declined.
Richard